NFPA 72 code sections · Signal Types & Monitoring
Silencing an alarm is allowed — forgetting it is not
The code permits a means to deactivate (silence) alarm notification appliances, but only if the system is attended or the AHJ permits it, and a subsequent alarm from a different initiating device or zone must re-activate the appliances. The silence must also be indicated at the panel, and the system cannot be left silenced indefinitely — a silenced alarm that nobody resets is treated as an impaired system. Alarm silence is for investigation, not a workaround for a nuisance detector.
NFPA 72 reference
Chapter 10 — Fundamentals
10.12 Alarm Signal Deactivation (10.12.1 means to deactivate; 10.12.3 subsequent alarm re-activates; silence indication)
References use NFPA 72 2019/2022 numbering — section numbers can shift between editions, so confirm in the edition your AHJ has adopted.
On the job
A restaurant manager silences the horns after a kitchen detector trips and leaves the panel in silence so the lunch rush can continue. A second detector activates in the dining room and, because the panel re-sounds on a new alarm, the room evacuates. Had the manager simply disabled the NACs, the second alarm would have been silent — the code difference between silencing and disabling.
Quick check
1. After alarm appliances are silenced, an alarm from a different zone or device must:
2. Alarm signal deactivation is intended for:
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